Patello-femoral joint disease is a condition in which the articular cartilage of the patella and/or the femoral trochlear groove is eroded due to osteoarthritis resulting in some cases in severe anterior knee pain. For patients with isolated patello-femoral joint disease who otherwise show no evidence of the disease present in the tibiofemoral joint, or for patients with a history of chronic patella dislocations, a patello-femoral joint replacement offers a beneficial alternative to total joint replacement. Moreover, a patello-femoral joint replacement provides pain relief or improved patella tracking while preserving significantly more bone than a total joint replacement.
In total joint replacement, portions of a patient's trochlear groove, medial and lateral condyles, and tibial plateau are generally resected. In patello-femoral joint replacement, generally only the patella and the trochlear groove are replaced. Bone preservation is an important consideration in opting for patello-femoral joint replacement for the patient. Other benefits of patello-femoral joint replacement in view of total joint replacement may include less cost as well as less rehabilitation time for the patient.
Current patello-femoral joint replacement systems employ different types of instruments that remove bone in the trochlear groove region of the femur. For instance, bone adjacent the intercondylar notch of the trochlear groove may be removed with an osteotome, rasp, reciprocating or oscillating saw, or burr, or more likely, with a combination of these known resection instruments in the art. However, there is very little control of the shape and depth of the resection made by these tools. Perhaps the biggest drawback of the instruments mentioned above is that each provides no true anatomically based means of restoring the trochlear groove or patella track to ensure proper patello-femoral kinematics. There is no systematic approach to ensure that the bone being resected will be replaced with a prosthesis that will be implanted on the resected bone.
During a procedure to restore the patella track of a patient in a patello-femoral joint replacement, it is important to ensure that the prosthesis that will be implanted does not restrict flexion of the knee by raising the patella anteriorly and/or effect the natural track of the patella by not accurately restoring the “Q angle” of the trochlear groove defined by the lines representing the pull of the quadriceps muscle and the axis of the patellar tendon.